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Book .lisiSL]^ 



UNITED STATES DEPARTMENT OF AGRICULTURE 




— /^V-V — 



t BULLETIN No. 1035 

Contribution from the Bureau of Entomology 
L. O. HOWARD, Chief 




Washington, D. C. 



PROFESSIONAL PAPER 



February 17, 1922 



V THE RED SPIDER ON THE AVOCADO. 

By G' F; Moznette, Assistant Entomoloyist, Tropical and Subtropical Fruit 

Insect Inrcstioations. 



CONTENTS. 



Page. 

Introduction 1 

Economic importance 1 

Nature of injury to foliage 2 

Food plants and distribution 2 

Description and haljits 4 

Biological data 7 



Page. 

Predatory enemies ;) 

Spraying experiments 11 

Spray rod versus spray gun 1:; 

Cultural methods in the grovo 14 

Recommendations 15 



INTRODUCTION. 

The red spider Tetranychus y other si McG. is one of the fore- 
most enemies of the avocado and attacks a number of other plants 
and fruit trees in Florida. It was recognized by avocado growers 
as an important enemy of this fruit as early as 1909, and since that 
time the damage caused by it has become more pronounced each 
year. This bulletin records the work with this spider during the 
years 1918 and 1919 and the results of cooperative spraying experi- 
ments in connection with the station established by the Bureau of 
Entomology in 1917 at Miami, Fla., for the investigation of various 
insect enemies of the avocado and other subtropical fruits character- 
istic of that region. 

ECONOMIC IMPORTANCE. 

In groves where the red spider is abundant the trees frequently 
become defoliated prematurely during the winter season. This 
generally results in an abnormal development of bloom the following 
spring and the weakened trees are unable to set and hold a full crop 

75523°— 22 




2 



BULLETIN 1035, U. S. DEPARTMENT OF AGRICULTURE. 



of fruit. To sustain the bloom and aid in the setting of fruit the 
older foliage should remain on the trees until a sufficient amount of 
new growth apparently arising from the inflorescence (fig. 1) has 
l)eon i:)roduccd in the spring to take its place. 

NATURE OF INJURY TO FOLIAGE. 

The red spider punctures the leaves and sucks the contents, forming 
Avhite spots at the point of attack. As these feeding punctures and 




Fic. 1. — .\vocado blossom cluster with older leaves which sustain the bloom, 
and developing new growth. 

resultant white spots become more in evidence a gradual burning and 
reddening of the foliage results, as if scorched by fire (PI. I, A, B). 
The foliage so attacked soon falls, irivin<r the tree a naked appearance 
(fig. 2). 

FOOD PLANTS AND DISTRIBUTION. 

This red spider was first named and described by PI A. McGregor ^ 
from specimens on camphor {Cinnajnomum campJiora) leaves sent 



^ McGregor, E. A. Four new tetranychids. In Ann. Ent. Soc. Amer., v. 7, no. 4, 
p. ."^55-357, 1914. 



LIBRARY' pi? CONGRESS 



Bui. 1035, U. S. Dept. of Agriculture. 



Plate I. 




The Red Spider of the Avocado 

A, Avocado leaf with characteristic reddening and scorched appearance caused by 
the red spider ; B, Uninjured avocado leaf. 



THE EED SPIDER ON THE AVOCADO. 



him in 1914 by W. W. Yotlieis, of Orlando, Fla. The Avriter has found 
it attacking both the West Indian and Guatemalan varieties of 
avocados {Persea gmtisshna), being particularly injurious to the 
more tender West Indian types. It occasionally causes considerable 
injury to the mango {Mangifera indica) and in many sections of 
northern Florida to the cam])hor and Australian silk oak [GreviUea 




Flu. 2. — Defoliated avocado troe diiriug midwinter, tlie result of attacks on 
foliage by the red spider. 

rohusta), to the foliage of which it imparts the same discoloration 
that it causes to the avocado. It has also been collected in Florida on , 
a species of eucalyptus {liucali/ptus sp.). In addition to these host 
])lants, the writer has at times collected the red spider on Terminalia 
((rju}ia, Anno)ta squamosa, Cucujnis sativus, and Icacorea paniculata — 
the latter a plant growing quite commonly in the hammocks of south- 
ern Florida. 



4 BULLETIN 1035, V. S. DEPARTMENT OF AGRICULTURE. 

Mr. E. A. McGregor reports it as attacking also the American elm 
{ZJlmus americana) and two other varieties of elm {ZJlmus spp.), 
the willow (Salix sp.), the white oak (Qiiercus aiha), and the pecan 
( Hicoria pecan) , at Batesburg, S. C. He records it also on elm ( Ulmus 
<p.) from Columbia. S. C, and Laiirinburg, X. C. These records in- 
dicate a probable wide distribution of this red spider through the 
South. In Florida the writer has found this species along both the 
cast and west coasts, including Miami Beach, Miami, Biscayne Key. 
Homestead, West Palm Beach, Florida City, Fort Myers, Braden- 
town, Oneco, and Winter Haven. 

DESCRIPTION AND HABITS. 



THE ADULT FEMALE. 



In appearance the adult female (fig. 3, /) is similar to most red 
spiders which attack vaiious other crops. It is small, of a rusty red 






Fig. 3. — The avocado nd spider : a. b. Egg; c, larva ; d, first nymph ; e, second 
nymph ; f, adult female. 

color, averaging 0.30 mm. in size. The abdomen joins the cephalo- 
thorax, formed by the fusion of the head and thorax, at its full width 
and extends over the portion to which the posterior pair of legs is 
attached. The body and legs are covered with bristles. 

THE MALE. 

The body of the male is slender and pointed toward the tip of the 
abdomen and is somewhat smaller than that of the female. The legs 
are slightly darker and longer than those of the female. The eyes 
are red and somewhat more conspicuous than those of the female. It 
averages 0.22 mm. in length. 



THE RED SPIDER ON THE AVOCADO. 5 

THE, EGG. 

The egg- {^g. 3, a,h) is ^lobose in shape, smoky amber in color, and 
bears a stalk at its apex. Guy fibrils are occasionally seen connecting 
the egg with the leaf. 

The eggs are deposited singly and when the leaf first becomes in- 
fested are generally found located along the midrib at the base of the 
leaf. As the activities of the mites increase with succeeding genera- 
tions, the eggs may be found scattered over the entire leaf. 

The incubation period varies according to the temperature and gen- 
eral climatic conditions. (See Table 1.) During midwinter, with 
mean daily temperatures between 00° and 70° F., incubation requires 
from 7 to 11 days. During April and Maj^ the incubation period 
averaged from 4 to 5 days with mean temperatures between 70° and 
80° F., in rearing experiments with this species. In hatching, the 
shell of the egg splits more or less completely around and the larva 
easily extricates itself. During the height of the red spider season 
leaves will be observed heavily covered with hatched eggshells which 
adhere to the leaf and impart to it a whitish cast. 

Table 1. — Length of the epy stadiitin. 



No. 


Date de- 


Date 


Dura- 


Mean 


No. 


Date de- 


Date 


Dura- 


Mean 


posited. 


hatched. 


tion. 


ature. 


posited. 


hatched. 


tion. 


ature. 








Days. 


° F. 








Days. 


° F. 


1 


Oct. 15 


Oct. 20 


5 


78 


7 


Jan. 21 


Feb. 1 


11 


60 


2 


Oct. 22 


Oct. 26 


^ 


77 


8 


Feb. 15 


Feb. 22 


7 


70 


3 


Nov. 8 


Nov. 13 





72 


9 


Mar. 15 


Mar. 20 


a 


72 


4 


Nov. 30 


Dec. 8 


8 


70 


10 


Apr. 1 


Apr. 5 


4 


75 


5 


Dec. 18 


Dec. 25 


7 


65 


11 


May 31 


June 5 


5 


76 


6 


Jan. 1 1 Jan. 11 


10 


58 


12 


July 11 


July 15 


4 


79 



THE LARVA. 



The newly hatched larva {fig. 3, c) is round, very light yelloAv. 
]}ossesses six legs, and in size does not exceed that of the egg from 
Avhich it emerged. It is very delicate, and a marked characteristic 
is its possession of conspicuous carmine eyes. During the process of 
development and feeding the young creatures commence to change 
color. The larva measures 0.17 mm. in length on an average. 

As with practically all mites the larva stage is divided into an 
active and a quiescent period. The former is passed while the larva 
is feeding and the latter in preparation for the first molt. The 
time spent in the quiescent period of the larva stage averages in most 
instances only a few hours. The average length of the larval period 
is 2.58 days. 



BULLETIN 1035, U. S. DEPARTMENT OF AGRICULTURE. 
Table 2. — Length of the kirntl sstoflinm. 



No. 


Date of 


Date 


Dura- 


Mean 


No. 


Date of 


Date 


Dura- 


Mean 


hatching. 


molted. 


tion. 


temper- 
ature. 


hatching. 


molted. 


tion . 


temper- 
ature. 








Day.1. 


°F. 








Days. 


'F. 


1 


Oct. 18 


Oct. 20 


2 


76 


7 


Feb. 1 


Feb. 4 


3 


65 


2 


Oct. 28 


Oct. 31 


3 


77 


8 


Feb. 22 


Feb. 24 


2 


70 


3 


Nov. 1.5 


Nov. 19 


4 


75 


9 


Mar. 20 


Mar. 23 


3 


72 


4 


Dec. 10 


Dec. 13 


3 


70 


10 


Apr. 5 


Apr. 7 


2 


75 


5 


Dec. 2.') 


Dec. 28 


3 


(iS 


11 


June 5 


June 7 


2 


76 


6 


Jan. 11 


Jan. 15 


4 


63 


12 


July 13 


July 15 


2 


79 



THE FIRST NYMPHAL STAGE (THE PROTONVMPH). 

The first nymphal sta^e (fig. 3, (/) differs from the larva in having 
four pairs of legs instead of three and is slightl}' increased in size. 
The extra pair of legs appears behind the last pair of legs of the 
larva. The segments of the legs become longer, as do likewise the 
bristles on the body and legs. The color of the body darkens. The 
abdomen in this stage becomes elongated as compared to the larva. 
The average length of the protonymph is 0.25 mm. 

For the most part the habits of the nymphal stage are similar to 
those of the larva. As Avith the larval stage the protonymph stage is 
divided into an active feeding period and a quiescent period prepara- 
tory to molting. The average length for the first nymi)hal stage is 
2.8 days. 

Tablk 3. — Length of the first nifiiipltul .stadiuiii. 





Date 


Date 


Dura- 


Mean 


No. 


Date 


Date 


Dura- 


Mean 


No. 


emerged. 


molted. 


tion. 


temper- 
ature. 


emerired. 


molted. 


tion. 


temper- 
ature. 








Days. 


"F. 






Days. 


^F. 


1 


Oct. 20 


Oct. 22 


2 


76 


7 


Feb. 4 


Feb. 6 


9 


65 


2 


Oct. 31 


Nov. 3 


3 


77 


8 


Feb. 24 


Feb. 2(> 


2 


70 


3 


Nov. 19 


Nov. 23 


4 


75 


9 


Mar. 23 


Mar. 25 


2 


72 


4 


Dec. 13 


Dee. 18 


5 


70 


10 


Apr. 7 


Apr. 9 


2 


75 


5 


Dec. 2S 


Jan. 1 


4 


68 


11 


.June 6 


June N 


2 


76 


6 


Jan. 15 


Jan. 18 


3 


63 


12 


July 14 


July 16 


2 


79 



THE SECOND NYMPHAL STAGE (THE DEUTONYMPH). 

The second nymphal stage (fig. 3, e) is similar to the first nymphal 
stage except that it is much larger and more elongate. In its full- 
grown condition, however, it resembles more the adult, though the 
color is not as deep a red. It averages 0.38 mm. in length. 

The habits of the second nymphal stage are likewise similar to those 
of the larva stage. The average length for the second nymphal stage 
is 2.84 days. 



THK rtKD SPIDER ON THE AVOC'ADO. 
Tabi.k 4. — Length of the second nymphal stadium. 



. No. 


Date 
emerged. 


Date 
molted. 


liura- 
tion. 


Mean 
temper- 
ature. 


No. 


Date 
emerged. 


Date 
molted. 


Dura- 
tion. 


Mean 
temper- 
ature. 


1 
2 
3 

t 

6 


Oct. 22 
Nov. 3 
Nov. 23 
Dec. is 
Jan. 1 
Jan. IS 


Oct. 25 
Nov. 6 
Nov. 25 
I>ec. 21 
J an . 4 
Jan. 24 


Days. 
3 
3 
2 

3 
3 
3 


T. 
76 
77 
75 
70 
fi8 
(i3 


S 
9 
10 
11 
12 


Feb. 6 
Feb. 2t> 
Mar. 25 
Apr. 9 
June 8 
July Ifi 


Feb. 10 
Fob. 29 
Mar. 28 
Apr. 12 
June 10 
July 18 


4 
3 
3 
3 

2 


65 
70 
72 
75 

76 
79 



BIOLOGICAL DATA. 

Webhhig. — Unlike the majority of red spiders this species does not 
spin an extensive weh and carries on its depredations on the foliage 
practically unprotected. The only indications of any webbing made 
by this species are the mere fibrils attached to the apex of the eggs 
Avhen deposited (fig. 3, a). 

Average length of life period. — The length of the life period of the 
adult mites varies greatly with the season and temperature and possi- 
bly other conditions. Experiments on the life history of this species 
shoM^ed that adults emerging November 25 came to their natural 
death during the period January 1 to 15, while those emerging Junt> 
10 succumbed between July 1 and 15. This shows that during the 
dry winter months approximately two months are required from the 
time of emergence to the completion of the life period, while during 
the humid summer months approximately a month is required. 

Molting process. — Before molting the mite securely attaches itself 
to the leaf. In emerging from the quiescent stage the old skin splits 
transversely along the cephalothoracic-abdominal suture. Following 
the splitting of the skin the anterior end of the mite is slowlj'^ drawn 
from the old skin. AVitli the use of its fore legs the mite forces its 
way out from the shell. 

Pafthenogenesis. — Some immature individuals were isolated on a 
number of plants. From these individuals virgin females were ob- 
tained. These females produced eggs and in each instance the re- 
sultant individuals were males. 

Migration. — There does not seem to be an alternate host of this spe- 
cies. Individual red spiders may be found on the avocado at any time 
during the year in varying numbers, and never leave the tree for want 
of a new or alternate host plant on which to feed. In a grove the red 
spiders are spread from tree to tree by the wind, birds, etc. 

Generations of the species. — The generations of the avocado red 
spider fluctuate as to number and overlap considerably. In years of 
little rain during the fall the red spiders come in evidence more 
quickly than when rains occur earlier. Intermittent rains frequently 



8 



BULLETI:N 1035, U. S. department of AGRldULTT'Ri:. 



occurring' during the red spider season also interfere with the regu- 
larity of the generations. Activity of the red spider usually com- 
mences during the latter part of August and ceases the first part of 
April, giving an active season of about 240 days. The average dura- 
tion of the life cycle is 14.2 days, which would give 17 generations. 
This would be true where no interruptions due to climatic conditions 
occurred, and when no other factors interfered with the normal activi- 
ties of the mites in the field. 

Shedding of the foliage. — During the winter months the foliage 
may be termed " dormant," no new^ growth being present on the trees. 
Usually during the latter part of March and April the avocado com- 
mences to bloom and the older leaves, which have served their purpose 
to the trees, commence to fall. With the shed leaves many mites are 
lost and do not regain positions on the trees. During the latter part 



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Fig. 4. — Curves showing 2-yGar composite soasonal status of the avocado red spider la 
southern Florida. The decimations arising through the amount of preiipitation are 
the most importani controlling factor in tlie activities of the species. 

of April very little old foliage is present and a remarkable reduction 
of red spiders is apparent. A fcAv old leaves, however, always re- 
main on the trees until the newer growth has hardened and thus 
enable the red spiders to remain continuously on the trees and to in- 
fest the newer growth when it hardens. 

Climatic control. — Climatic conditions existing in Florida influence 
the development and activity of the red spicier to a marked degree. 
This particular species, as has already been stated, confines its depre- 
dations to the upper surface of the foliage. The species so working 
is exposed to the weather conditions. Hence during the period of 
the life cycle or seasonal cycle there is a series of fluctuations in 
numbers. In April, as the rainy season approaches, the red spider 
barely maintains existence. (Fig. 4.) During the months of June. 
July, and August no pronounced gain is made, but toward the latter 
part of October the avocado ceases to produce new growth, the red 
spiders commence to make their appearance in greater numbers, and 
increase during November and December. They usually reach the 
maximum number during January and February, and decrease 
again toward March. Precipitation is the one climatic factor im- 
jDortant in reducing the red spiders during the spring and summer. 



THE RED SPIDER ON THE AVOCADO. 



9 



(Fig. 5.) Durino; the summer in Florida drenching and frequent 
rains usually prevent the red spiders from establishing themselves 
on the trees. During late fall and winter and early spring it rains 
seldom, and the interference with the activities of the red spider is 
slight. 

PREDATORY ENEMIES. 

A number of predatory enemies of the avocado red spider aid at 
various times in keeping down the species on the avocado to a small 
degree. 



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Fig. 5. — Precipitation chart for the yrars 1918 and 1019 in southern Florida. 

Scolothrijis semnaculatus Pergande is one of the predatory thrips 
and is not abundant during the height of the red-spider season. 
Nevertheless it is present doing its share of destruction. It is a light- 
colored thrips possessing six dark spots on its body. It feeds on the 
red spiders in both the larva and adult stages. 

ClirysoiKi JateiaViH Guer. is one of the so-called lace- wing flies and 
is predatory in the larva stage on the red spider. The larvte, while 
feeding and wandering about the foliage in search of their prey, 
carry with them a protection consisting of foreign material, such as 
cast red spider skins, etc. The larA^se have a voracious appetite and 



10 



BULLETIN 103"), U. S. DEPARTMENT OF AnRICULTUEE, 



possess powerful jaws with which they attack their prey. This 
species is quite beneficial. 

Scymnus utilis Horn. — The most important enemy of the red 
spicier found up to this time is a very small black ladybird beetle 






Fig. fi. — ficiimnuK utilis: a. Larva: b, pupa; c. adult. Greatly enlarged. 

(fig. 6, c) about Vij-iiit'h long. With the beetles may be found their 
dark brown larvEe (fig. 6. a), also feeding on all stages of the red 
spider. 

Seymiiu-H klnseli Casey is another ladybird beetle found feeding in 
both the larva and adult stages on the red spider. It is larger than 




Fir 



-Lcptothrips mali: Adult thrips. Cieatl.v enlarged. 

the former, the abdomen is black, and the head reddish. It is not 

a very abundant species and is not as beneficial as the former beetle. 

Leptothrips mali Hinds is a large black thrips (fig. 7) predatory 

in both the larva and adult stages, and when present is very acti^-e 



THE RED SPIDER. ON THE AVOCADO, 



11 



on the foliage in searc-li of red spiders. It is not very abundant at 
any time. 

SPRAYING EXPERIMENTS. 

A number of insecticides have been tried out to ascertain their rela- 
tive merits against the avocado red spider. The experiments Avere all 
conducted cooperatively with growers and in groves where the mite 
was abundant. 




Fiu. 8. 



-Power duster in operation using sulphur dust against the red spider iu an 
avocado grove. 



SULPHUR DUST. 

An impalpable sulphur dust was tested on both the West Indian 
and Guatemalan races of avocadoes. In applying the material a 
power duster (fig. 8) was used. The sulphur proved to be very 
effective against the species, killing 99 per cent of the spiders, and 
remaining effective on the foliage over as long a period as did any of 
the liquid sprays tested. Experiments Avith this material showed that 
it was not necessary to apply the sulphur dust when the foliage was 
wet with dew. IMiero an avocado grower has a large acreage and 
the red spider is the only serious enemy to contend with, the dusting 
method is very practical and by far the quicker method. At the 
present time, however, the avocado grower has other insect pests with 



12 BULLETIN 1035, U. S. DEPARTMENT OF AGRICULTUKE. 

Tvhich lie has to contend, making it necessary to use liquid insecticides 
in combination with a sulphur spray in some form for their control. 
Up to this time the writer has not found it practical to use a combina- 
tion of sulphur dust and 40 per cent nicotine sulphate against the 
insects of the avocado. iSil^iiM ,i.. 

LIME-SULPHUR CONCENTRATE; 

In using lime-sulphur concentrate spray on the avocado a number 
of strengths were tried, e. g., 1 gallon of concentrate to 40 gallons 
of water, 1 to 60, and 1 to 75. In spraying with lime-sulphur solu- 
tion it was found through actual count that nothing is to be gained in 
applying too strong a solution of lime-sulphur to red spiders on the 
avocado. A strength of 1 gallon of the concentrate to 60 gallons of 
water proved to be the most efficient, generally killing 99 per cent 
of the spiders and producing sufficient body as a spray on the foliage 
to remain effective during the dry season against later hatching 
young. Under certain conditions applications of 1 to 40 and 1 to 60 
were too strong, and considerable damage resulted to the foliage from 
burning, especially on the south side of the trees. When the tem- 
perature is above normal during the winter season, or when the trees 
do not attain a thoroughly dormant condition, a strength of 1 gallon 
of the concentrate to 75 gallons of Avater was found satisfactory. It 
was also ascertained that it is not necessary to incur the extra expense 
of adding a spreader of lime-suli)hur spray, such as flour paste, glue, 
or fish-oil soap, because good results were obtained without it. 

COMMERCIAL SODIUM SULPHID. 

Commercial sodium sulphid was used at a strength of 2 pounds to 
50 gallons of Avater. It was ascertained that this spray killed approxi- 
mately 95 per cent of the red spiders present. Because of its chemical 
composition, however, the spray did not dry thoroughly on the foli- 
age. The hydroscopic condition so formed permitted the spray cover- 
ing the eggs and foliage to be readily washed off by succeeding rains, 
and nothing remained to destroy the hatching young. 

NICOTINE SULPHATE CONTAINING 40 PER CENT NICOTINE. 

At times the red spiders make their appearance during the fall 
before the fruit is picked. At this time it is not advisable to use 
any of the sulphur sprays, as they adhere to and discolor the fruit. 
By using 40 per cent nicotine sulphate at the rate of 1 part to 900 
parts of water, with the addition of 2 or 3 pounds of fish-oil soap to 
each 100 gallons of the diluted spray as a spreader, satisfactory re- 
sults were secured. The spray, however, proved to be effectiA^e only 



THE RED SPIDER ON THE AVOCADO. 



13 



temporarily, as none remained on the foliage to destroy the young 
on hatchinfr. 



SPRAY ROD VERSUS SPRAY GUN. 

In making a comparison of the spray rod (fig. 9) and the spraj^ 
gun (figs. 10 and 11) it was found that the latter gave better satis- 
faction against the red spider. Where an orchardist is short of help 
considerable benefit can be derived by using the spray gun, as the 
spray operator can cover the ground much faster than when using 




Fig. 9. — Spraying in an avocado gi-ove witli spray rods. 

the spray rod. As the red spider works on the top of the foliage the 
operator can stand off a short distance from the tree, and with the 
use of the spray gun can spray from the bottom to the top of the 
tree by turning the handle of the gun which changes the sj^ray from 
the fan or fog spray (fig. 10) to a long-distance spray (fig. 11). 

The writer has found that growers in using the spray gun often 
neglect to change the disk in the nozzle frequently enough and won- 
der why they can not maintain sufficient pressure while spra3ang. 
The operator should watch the opening of the disk in the nozzle of 
the gun, and should replace it when it is worn. 



14 BULLETIN 1035, U. S. DEPARTMEXT OF AGRICULTURE. 

CULTURAL METHODS IN THE GROVE. 

Clean culture does not play an important part in the control, as 
this species does not infest weeds or plants in or about avocado 
groves. Orchards mulched in various ways in southern Florida 
were found to be less infested with the red spider as a rule than those 
Avhere clean culture w^as practiced. The avocado seems to thrive 
better where mulching is practiced and the moisture is conserved. 
Red spiders generally like dry conditions such as are afforded in 





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Fig. 10. — Spraying in an avocado gi'ove with spray gun, using the fan or big fog spray. 

groves where clean culture is followed. This is especially evidenced 
in seasons of drought during the year. 

One factor which influences greatly the abundance and appearance 
of the red spider in a grove is the vitality of the trees. Nothing is to 
be gained by allowing trees to suffer from w^ant of proper attention 
in the way of mulching, plant foods, and culture. Where growers are 
in doubt about the proper procedure to use in caring for their avocado 
trees, they should get in touch wdtli either the Plant Introduction 
Garden maintained by the United States Bureau of Plant Industry 
at Miami, Fla., or their particular county agent. 



THE RED SPIDER ON THE AVOCADO. 



15 



RECOMMENDATIONS. 

The presence of the avocado reel spider on the trees in considerable 
numbers while the foliage is still green should be a sufficient indica- 
tion of impending injury to cause the grower to begin immediate 
application of control measures. The grower should not wait until 
the foliage attacked becomes noticeably brown prematurely and 
begins to drop. 

During the winter after the fruit has been picked use the liquid 
lime-sulphur 1 to GO. When the temperature is above the normal and 
the trees do not attain a thoroughly dormant condition the liquid 
lime-sulphur should be reduced to 1 to 75. 







^4-4- 







I'm. 11.-- Spiayiu^ in an avocado ^rove witli spray guu, using tli. long distance spray. 

If the red sj^iders are present while the fruit is still unpicked in 
the fall, 40 per cent nicotine sulphate 1 to 900. with the addition of 
2 or 3 pounds of fish-oil soap to each 100 gallons of the diluted spray, 
will give temporary relief and will not discolor the fruit. 

Thorough application is a most essential point in combating the 
red spider. — If haphazard work is performed and much of the 
foliage left unsprayed, such infested foliage serves as a source of 
reinfestation to the tree, and the mites will be more in evidence after 
application than when thorough work has been done. 



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